5/16-18 UNC HSS Spiral Flute Tap – TiN Coated
TiN-coated 5/16-18 UNC HSS spiral flute machine tap for blind-hole internal threading. The helical flute geometry carries chips back toward the shank, helping reduce chip accumulation in enclosed holes, while the 18 TPI UNC thread specification supports common inch-thread machining and replacement requirements.
Product Specifications
10 Pieces
1–3 Days for In-Stock Items
Dimensions / Thread Tolerance / Coating / OEM
Consistent Quality
Consistent geometry across repeat orders.
Flexible Orders
Small batches and mixed sizes available.
OEM Support
Custom marking, labels and packaging.
Standard & Custom
Standard sizes and custom configurations.
5/16-18 UNC HSS Spiral Flute Tap – TiN Coated
This 5/16-18 UNC HSS spiral flute tap is designed for blind-hole internal threading where controlled chip evacuation is important. The helical flute geometry carries chips back toward the shank and out of the hole, helping reduce chip packing near the bottom during machine tapping. A TiN coating provides a wear-resistant surface for repeated threading operations, while the standard 5/16-18 UNC specification provides an 18 TPI coarse Unified thread for general industrial components. Confirm the workpiece material, pilot-hole size, required full-thread depth, thread tolerance and machine conditions before production.
Key Configuration
Helical flutes guide chips back toward the shank, helping clear material from blind holes where chips cannot pass through the bottom.
The tool cuts a 5/16-inch Unified National Coarse internal thread with 18 threads per inch for standard UNC applications.
The TiN-coated HSS cutting surface is intended to improve wear resistance and support repeatable machine tapping under suitable cutting conditions.
Key Product Advantages
Blind-Hole Tapping
Spiral flute geometry helps remove chips upward from enclosed holes during internal thread cutting.
Wear-Resistant Coating
TiN provides a hard coated surface that can help reduce wear under properly selected tapping conditions.
Standard 18 TPI Pitch
The standard 5/16-18 UNC specification simplifies matching to common inch-thread drawings and replacement requirements.
Machine-Tapping Configuration
Suitable for synchronized machine tapping when pilot-hole size, lubrication, alignment and cutting data are correctly controlled.
Tapping Applications
This 5/16-18 UNC spiral flute tap is intended primarily for blind-hole threading on tapping machines and CNC equipment. The current product information lists carbon steel, stainless steel, aluminum and alloy materials as possible workpiece groups, but the exact grade and hardness should be confirmed before selecting production cutting conditions.
Blind-hole tapping requires enough extra hole depth for the tap lead and chip space. Confirm the pilot-hole diameter, required full-thread depth, workpiece grade, thread tolerance, lubrication and synchronized feed before production.
Workpiece Material Selection
| MATERIAL GROUP | TYPICAL EXAMPLES | SELECTION NOTE |
|---|---|---|
| P Steel | Carbon and alloy steels | Confirm grade and hardness |
| M Stainless Steel | Selected stainless steel grades | Application-specific review recommended |
| N Non-Ferrous | Aluminum and selected non-ferrous alloys | Confirm chip behavior and lubrication |
The current product description identifies steel, stainless steel, aluminum and alloy materials as potential applications. This does not establish universal suitability for every grade or hardness. Confirm the actual material before setting cutting speed and lubrication.
Product Details & Demonstration
The product image and video below show the 5/16-18 UNC TiN-coated spiral flute tap configuration. Confirm thread tolerance, tap dimensions and machine requirements when ordering.
Product Video
For additional machine-tapping configurations, browse our HSS Tap Range.
Thread Specification & Tool Configuration
This product is a single-size 5/16-18 UNC spiral flute machine tap. The nominal thread diameter is 5/16 inch (0.3125 in / approximately 7.94 mm) with 18 threads per inch, corresponding to a pitch of approximately 0.0556 in / 1.411 mm. The supplied product information confirms HSS construction, TiN coating and a spiral flute configuration intended for blind-hole tapping. Dimensions such as overall length, thread length, shank diameter, square size, flute count and thread-fit class should be confirmed before ordering.
| Specification | Value |
|---|---|
| Thread Size | 5/16-18 UNC |
| Thread Standard | Unified National Coarse (UNC) |
| Nominal Diameter | 0.3125 in / ≈7.94 mm |
| Threads per Inch | 18 TPI |
| Thread Pitch | 0.0556 in / ≈1.411 mm |
| Tap Type | Spiral Flute Machine Tap |
| Tool Material | HSS |
| Coating | TiN |
| Primary Application | Blind-Hole Tapping |
| Chip Evacuation | Toward the shank / out of the hole |
Pilot-hole confirmation: Do not select the pre-drill diameter from nominal thread size alone. Confirm the required thread percentage, finished-thread tolerance and workpiece material before production, particularly for stainless steel and other high-torque applications.
Application & Setup Checks
5/16-18 UNC Tap Speeds & Feed Settings
Use the HSS tapping chart below as a general starting reference only. Final spindle speed should be selected according to the workpiece grade and hardness, TiN-coated tap condition, blind-hole depth, lubrication, machine rigidity and required thread quality.
Setting Speed & Feed
Thread pitch: 5/16-18 UNC has 18 threads per inch, so synchronized feed per revolution is approximately 0.0556 in/rev, or 1.411 mm/rev.
Inch feed rate: Feed in inches per minute = RPM ÷ 18.
Metric feed rate: Feed in mm/min = RPM × 1.411.
For additional reference, see our HSS cutting tools speeds & feeds guide.
For other UNC, blind-hole and machine-tapping options, browse our HSS Tap Range.
For general tool selection, see How to Choose HSS Cutting Tools.
View HY Taps Catalog — for additional HSS tap series and thread configurations.HSS Tap Customization
For requirements beyond the standard range, send your tap drawing or application details. Custom HSS cutting and forming taps can be reviewed for the following specifications.
| PARAMETER | CUSTOMIZATION OPTIONS |
|---|---|
| Thread Specification | Metric, UNC/UNF and pipe threads; special diameters, pitches and left-hand threads. |
| Thread Accuracy | Tap limits and oversize allowances to suit the required internal-thread tolerance and gauging requirements. |
| Tap Geometry | Straight flute, spiral flute, spiral point or forming design; chamfer and working geometry matched to the application. |
| Length & Reach | Overall length, threaded-section length and neck clearance to suit thread depth and component access. |
| Shank & Drive Square | Shank diameter, square dimensions and holding length to match the tapping holder. |
| Material & Surface Finish | HSS or cobalt HSS grades; uncoated, TiN or TiCN options, depending on the tap design and workpiece material. |
Options depend on tap type and size. Final specifications, minimum order quantity and lead time are confirmed with the quotation.
OEM & Private Label
Customer branding and packaging can be specified for distributor and tooling-brand orders.
Laser marking: Logo, thread size, product code and batch identification, subject to available shank space. Labels & packaging: Protective tubes, product labels and branded packaging to the approved artwork.
For a quotation: Send a drawing or thread specification, required tolerance, workpiece material and hardness, blind or through-hole details, thread depth and quantity. Include machine, holder and lubrication details for application-specific requests.
HSS Tap Quality & Inspection
HSS cutting and forming taps are checked against the confirmed product specification or approved drawing. Material verification, in-process dimensional checks and final inspection focus on thread accuracy, tool geometry and consistent identification before packing.
Key Inspection Points
Inspection items and acceptance criteria depend on the tap type, size and agreed requirements.
| INSPECTION ITEM | CHECK POINTS |
|---|---|
| Material & Hardness | HSS or cobalt HSS grade and material records; hardness requirements and verification agreed for the selected grade. |
| Thread Form & Accuracy | Thread size, pitch, profile and specified tap limits against the confirmed specification or drawing. |
| Working Geometry | Flutes, spiral point and cutting edges for cutting taps; forming lobes and lubrication grooves, where present, for forming taps. Chamfer geometry checked for each design. |
| Tool Dimensions | Threaded-section length, overall length, shank diameter and drive-square dimensions. |
| Runout & Surface Condition | Specified runout, burrs, chipped edges and visible defects on cutting or forming surfaces. |
| Coating & Identification | Specified surface finish or coating, visible condition, tool marking and label accuracy. |
Inspection documentation: Specify any required material records, dimensional reports or sample-thread validation before ordering. Availability and inspection scope are confirmed with the quotation.
Packaging & Batch Identification
Individual protective packaging helps prevent damage to tap threads and working surfaces. Labels identify the tool specification and order or batch reference. Models, quantities and packing details are checked before dispatch.
Export Packing & Delivery
Outer cartons, cushioning and export packing are selected for the order quantity and shipping method. Dispatch dates, freight and payment terms are confirmed with the order.
FAQ & Technical Support
Selection, blind-hole preparation, machine setup and ordering guidance for the 5/16-18 UNC TiN-coated HSS spiral flute tap.
Product & Application FAQs
What thread does this tap produce?
This tap produces a 5/16-18 UNC internal thread. The nominal diameter is 5/16 inch, or approximately 7.94 mm, with 18 threads per inch. The corresponding pitch is approximately 0.0556 inch or 1.411 mm.
Why is a spiral flute tap suitable for blind holes?
The helical flute geometry carries chips back toward the shank and out of the hole. This helps reduce chip packing near the bottom of a blind hole, where chips cannot exit through the opposite side of the workpiece.
How deep can I tap a blind hole?
The usable full-thread depth depends on the tap’s thread length and chamfer or lead geometry. The drilled hole must also provide additional bottom clearance for the tap lead and chip space. Confirm the required full-thread depth and actual tool dimensions before production.
What is the benefit of the TiN coating?
TiN provides a hard, wear-resistant surface on the HSS tap and can help reduce cutting-edge wear under suitable machining conditions. Actual tool life still depends on the workpiece material, pilot-hole size, tapping speed, lubrication, alignment and thread depth.
Which workpiece materials can this tap be used for?
The current product information lists carbon steel, stainless steel, aluminum and alloy materials as potential applications. Because chip behavior, hardness and tapping torque vary by grade, confirm the exact workpiece material before selecting the pilot-hole diameter and cutting conditions.
How should I choose the pilot-hole diameter?
Select the pilot-hole diameter according to the 5/16-18 UNC thread requirement, workpiece material, desired thread percentage and finished-thread tolerance. Do not select the pre-drill size from nominal diameter alone. Verify the drilled hole and inspect a trial thread before batch production.
Can this tap be used for through holes?
The spiral flute configuration is primarily selected for blind-hole chip evacuation. It may cut a through hole under suitable conditions, but a spiral point tap is normally a more application-specific choice when chips can be directed forward through an open hole.
What machine setup and tapping conditions are required?
Use accurate alignment, a compatible tapping holder, suitable lubrication and synchronized feed. For 18 TPI, feed per revolution is approximately 0.0556 inch or 1.411 mm. Spindle speed should be selected according to the workpiece material, tool condition and machine setup.
Ordering & Customization FAQs
What information is needed for a quotation?
Confirm the 5/16-18 UNC thread requirement, quantity, workpiece material and hardness, blind-hole depth, required full-thread depth and thread tolerance. Include machine, holder, coating, marking, packaging or dimensional requirements when applicable.
Can thread tolerance, dimensions or OEM branding be customized?
Custom thread tolerance, dimensions, tool material or coating options, laser marking and packaging can be reviewed according to the application and order quantity. Critical specifications should be confirmed before production.
Are sample orders available?
Sample orders can be reviewed before larger-volume purchasing. MOQ, stock availability and dispatch timing depend on the required quantity and any customized specification, coating, marking or packaging requirements.
Selection Guides
Use the HSS guide for general tool-material selection, compare tapping with thread milling where appropriate, and browse the HSS tap range for other UNC and machine-tapping configurations.
Catalog & Technical Downloads
HY Taps Catalog (PDF)General tap series reference. Use this product page’s Specifications & Sizes section for the 5/16-18 UNC thread and current product configuration; dimensions in other tap series may differ.
HSS Cutting Tools Speeds & Feeds Guide (PDF)General HSS tapping reference. Confirm cutting conditions for the actual workpiece and tool configuration. For 5/16-18 UNC synchronized tapping, feed per revolution is approximately 0.0556 inch or 1.411 mm.
Need Sizes, Pricing or Custom Options?
Send us the required tool type, sizes, quantities, workpiece material and any OEM or custom requirements. We will confirm suitable specifications, availability, lead time and quotation details.
Drawings, size lists and reference photos are welcome.
